Cleaning Systems and Methods for Rotary Screen Separators

ABSTRACT

A cleaning system for a screen of a rotary screen separator for processing feed material comprising liquids and solids has a housing, an air source, and a conduit system. The housing defines at least one housing chamber, at least one inlet opening, and at least one outlet slot. The conduit system is operatively connected between the inlet opening of the housing and the air source. Air flows from the air source through conduit system, through the inlet opening, into the housing chamber, and out of the housing chamber through the at least one outlet slot in at least one air flow stream extending along a flow plane. The housing is arranged relative to the screen of the rotatory screen separator such that the air flow stream impinges on the screen to remove debris from the screen.

PRIORITY CLAIM

This application is a continuing application and claims its priorityfrom the Utility application Ser. No. 14/726,848 filed Jun. 1, 2015,which, in turn claims priority from and entirely incorporates the U.S.Provisional Application filed as Ser. No. 62/005,910 filed May 30, 2014by David DeWaard.

FIELD OF INVENTION

This disclosure relates to the field of rotary separators used toseparate effluent into different fractions depending upon the diameterof the solid components and, more particularly, to systems and methodsfor cleaning the screens of such rotary separators during operation.

BACKGROUND

Rotary screen separators are often used to process effluent such aswaste from a dairy operation. Generally speaking, rotary screenseparators separate a feed material into solid and liquid components bydisplacing the feed material along a first side of a screen such thatsolid material remains on the first side and liquid material passesthrough perforations in the screen to a second side thereof.

Conventionally, rotary screen separators employ a screen having screenopenings for maintaining solids within the screen and allowing water topass through the screen. Solids can accumulate on the screen andinterfere with the separation of solids from liquids.

The need exists for an improved rotary screen separator that optimizesthe removal of solids and water from a feed material.

SUMMARY

The present invention may be embodied as a cleaning system for a screenof a rotary screen separator for processing feed material comprisingliquids and solids, the cleaning system comprising a housing, an airsource, and a conduit system. The housing defines at least one housingchamber, at least one inlet opening, and at least one outlet slot. Theconduit system is operatively connected between the inlet opening of thehousing and the air source. Air flows from the air source throughconduit system, through the inlet opening, into the housing chamber, andout of the housing chamber through the at least one outlet slot in atleast one air flow stream extending along a flow plane. The housing isarranged relative to the screen of the rotatory screen separator suchthat the air flow stream impinges on the screen to remove debris fromthe screen.

The present invention may also be embodied as a rotary screen separatorfor processing feed material comprising liquids and solids comprising ascreen, a drive system, at least one vane structure, and a cleaningsystem. The screen defines a longitudinal axis, an input port, and anoutput port. The drive system is for rotating the screen. The cleaningsystem comprises a housing, an air source, and a conduit system. Thehousing defines at least one housing chamber, at least one inletopening, and at least one outlet slot. The conduit system is operativelyconnected between the inlet opening of the housing and the air source.Operation of the drive system to rotate the separator causes the atleast one vane structure to displace the feed material along thelongitudinal axis. Air flows from the air source through conduit system,through the inlet opening, into the housing chamber, and out of thehousing chamber through the at least one outlet slot in at least one airflow stream extending along a flow plane. The housing is arrangedrelative to the screen of the rotatory screen separator such that theair flow stream impinges on the screen to remove debris from the screen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view from the output port end of a first examplerotary screen separator of the invention;

FIG. 2 is a cutaway side view of the first example rotary screenseparator;

FIG. 3 is a perspective view from the input end of the first examplerotary screen separator;

FIG. 4 is a perspective view of the underside of the first examplerotary screen separator from a first perspective;

FIG. 5 is a perspective hidden line view of the underside of the firstexample rotary screen separator from a second perspective;

FIG. 6 is a perspective detail view of the output end of a rotary screenseparator in one form;

FIG. 7 is a perspective top view of the first example rotary screenseparator;

FIG. 8 is a partial hidden line view of the input end of the firstexample rotary screen separator;

FIG. 9 is a perspective view of the underside of the first examplerotary screen separator;

FIG. 10 is a block diagram of a first example waste processing systemusing a rotary screen separator of the present invention;

FIG. 11 is a block diagram of the rotary screen separator of the firstexample waste processing system;

FIG. 12 is a cutaway side view of a second example rotary screenseparator;

FIG. 13 is a perspective detail view of the output end of a rotaryscreen separator depicting a first example outlet assembly of a cleaningsystem for the rotary screen separator;

FIG. 14A is a somewhat schematic end elevation section view illustratingthe use of the first example outlet assembly with a spray systemindicating a flow plane intersecting an exterior screen surface at afirst impingement angle θ and FIG. 14B is a somewhat schematic endelevation section view illustrating the use of the first example outletassembly with a spray system indicating a flow plane intersecting anexterior screen surface at a second impingement angle (3;

FIG. 15 is a perspective view illustrating the first example outletassembly;

FIG. 16 is a partial section view of an end portion of the first exampleoutlet assembly;

FIG. 17 is an elevation view looking along a plane extending through anoutlet slot defined by the first example outlet assembly;

FIG. 18 schematically depicts an example cleaning system employing anoutlet assembly such as the first example outlet assembly describedherein;

FIG. 19 is somewhat schematic end elevation section view illustratingthe use of the first example outlet assembly with a spray system;

FIG. 20 is a perspective view illustrating a second example outletassembly that may be used with a cleaning system of the presentinvention; and

FIG. 21 is an elevation view looking along a plane extending through anoutlet slot defined by the second example outlet assembly; and

FIG. 22 schematically depicts an example cleaning system employing ancontrol system to control operation of the blower.

DETAILED DESCRIPTION

A rotary screen separator is disclosed herein which may generallycomprise a frame and a rotating perforated screen supported by theframe. In one form, the rotating screen is horizontally aligned at aslight angle and often comprises an internal screw flight. The screwflight is operatively configured to reposition the media to be separatedfrom the input end of the separator to the solids discharge end. As thematerial moves through the screen separator, liquid and fine particlesare removed through the perforations in the screen.

The example hybrid rotary screen separator of the present inventioncomprises at least two separate regions each comprising a differentscreen size. In the example hybrid rotary screen separator disclosedherein, the perforations of the screen on the input end of the separatorcomprise a much finer hole size than the perforations toward the soliddischarge end. These regions of fine screen and coarse screen may beseparate structures which may be interconnected, or may alternatively bea unitary structure with separate regions of varying screen sizes alongthe length. In one form, these are connected to the same cylinder-likestructure.

The rotary screen separator of the present invention is adapted toprocess a high liquid content media (effluent) or feed materialcomprising both a solid component and a liquid component. As the feedmaterial enters the fine portion of the screen, a percentage of theliquid is removed. As the feed material transfers to the coarse portionof the separator, more of the liquid is allowed to escape, while much ofthe fine solids remain and are intertwined with the coarse solids in aconcentrated slurry.

In one example rotary screen separator of the present invention, theliquid escaping from or removed while the feed material moves throughthe fine portion comprises less solid content than the liquid escapingfrom or removed while the feed material moves through the coarseportion. The liquid removed in the fine portion and the liquid removedin the coarse portion define first and second filtrate streams,respectively. The separator of the present invention may be configuredsuch that the first and second filtrate streams exit or are removed fromthe separator by way of separate discharge ports should an operator wishto keep the filtrate streams separated for later processing.

Depicted in FIG. 1 is an axes system 10 comprising a vertical axis 12, atransverse axis 14, and a longitudinal axis 16. The axes system 10 is tobe used for description of the embodiments and is not per se part of thepresent invention.

FIGS. 1 and 2 illustrate that an example hybrid rotary screen separator20 of the present invention defines a system longitudinal axis A andgenerally comprises three major assemblies. The first assembly comprisesa housing 22 and a frame 24. This housing and frame assembly generallysupports and encloses the working portions of the separator 20.

The second assembly is the drive assembly 26 which generally comprises adrive motor 28, an optional reduction gear system 30, and a drive belt32 which is shown in FIG. 2. In FIG. 1, the drive belt 32 is covered bya protective shroud 34. The motor 28 may be coupled to the housing 22through a motor pivot 36 and drive tension adjuster 38.

The third assembly generally comprises a rotating screen 40. As will bedescribed in further detail below, the example rotating screen 40includes at least two different perforation regions. The examplerotating screen 40 also comprises at least one vane 42. In one form, therotating screen 40 is substantially cylindrical. The rotating screen 40may be driven by the drive assembly 26 and in one form rests upon aplurality of support rollers 44. The support rollers 44 may be held inplace, as shown for example in FIG. 1, by an outer flange 46 and aninner flange 48. Additional components, including additional supportrollers 44, will be described below with reference to FIGS. 2 and 5 atthe opposite longitudinal end of the separator 20.

To increase the portability of the separator 20, a plurality of liftingeyes 50 may be provided to facilitate connection of the separator 20 toa crane or the like (not shown) for moving and transportation thereof.Furthermore, a plurality of elevation adjusters 52 may be provided toallow the end user to adjust the elevation of the solid output end 54relative to the input end 56.

The example separator 20 further comprises an access door 58 in thehousing 22. The example access door 58 pivots between open and closedpositions about a plurality of access door pivots 60 to facilitateaccess to the interior portion of the housing 22. A handle 62 may beprovided for to facilitate lifting of the access door 58. The exampleaccess door 58 is further provided with a lid holder 64. The lid holder64 may be rotated from a storage position as shown in FIG. 1 to abracing position in which the lid holder 64 forms a strut that supportsthe access door 58 in an open configuration.

Several ports are formed on the lower portion of the separator 20. Onesuch port is a bypass outflow port 66, which will be described infurther detail below. A collection pan 68 may be provided at a bottomportion of the separator 20 to receive at least a portion of the fluidoutput from the rotating screen 40. The example collection pan 68defines a fine material output 70 and a coarse material output 72corresponding to the first and second filtrate streams, respectively,generally described above. As will be described in further detail below,the fluid output of or removed from the rotating screen 40 may bediverted to one of the fine material output 70 and the coarse materialoutput 72.

Referring now to FIG. 2, depicted therein is a cut away view of theexample separator 20 taken through the drive motor 28 and along thelongitudinal axis 16 and vertical axis 12. FIG. 2 further illustratesthat the vanes 42 form a screw flight 74.

As generally discussed above, the example rotating screen 40 generallycomprises at least two unique perforation regions. The example rotatingscreen 40 comprising two separate and distinct perforation regions;however, more than two unique perforation regions can also be utilized.

As feed material enters an example input port 76, the feed material ispressed towards a feed slot 78 (FIGS. 2 and 3). The feed materialeventually exits the feed slot 78 into a fine perforation region 80within the rotating screen 40. A portion of the liquid and some of thefine materials exit the interior of the rotating screen through theperforations in this fine perforation region 80. The material passingthrough the fine perforations generally redistribute toward a finecollection pan 82 and exit through the fine material output 70.

Coarser materials in the feed material that are not removed by therotating screen 40 in the fine perforated region 80, along with fluidremaining in the feed material, are displaced away from the input port76 by the screw flight 74 as the rotating screen 40 rotates about thelongitudinal system axis A. The coarser material and liquid remaining inthe feed material is thus displaced or otherwise redistributed towardthe output end 54 and thus enters a coarse perforation region 84. Moreof the fluids and a portion of the coarser materials remaining in thefeed material exit through the perforations in the coarse perforationregion 84 and are collected in the collection pan 68. The coarsematerials in one form reposition into the coarse collection pan 86,wherein they exit the separator 20 via the coarse material output 72.

The example rotating screen 40 is formed by two separate screens withdifferent screen sizes, and a seam 88 is formed in the example rotatingscreen 40 between the fine perforation region 80 and the coarseperforation region 84. Alternatively, the cylinder formed by therotating screen 40 may be formed from a single sheet of material andthus may be seamless.

A highly coarse portion of the feed material (i.e., has not exitedthrough the perforations in either the fine perforation region 80 or thecoarse perforation region 84) is displaced or redistributed toward theoutput end 54 and exits the separator 20 at a very coarse materialoutput 90. Typically, the highly coarse portion of the feed material iscollected at the coarse material output 90.

Adjacent to the example very coarse material output 90 are flanges 46and 48 that support an additional set of rollers or idler wheels 44 thatmaintain position of the rotating screen 40 as generally describedabove. The region of the rotating screen 40 between the flanges 46 and48 may comprise a solid region 92, which is generally not perforated. Atthe opposite end of the rotating screen 40, an outer flange 94 and innerflange 96 maintain position of the rotating screen 40 upon another setof idler wheels 98, which are also coupled to the frame 24.

This example separator 20 disclosed herein allows for feed material tobe processed at a much faster and more efficient rate than currentsingle screen separators of the same size. Tests have shown that aphysical implementation of the example separator 20 having a rotatingscreen 40 of approximately 3 feet in diameter and 10 feet in length thatrotates in a first range of approximately 6 to 8 rpm can separate orprocess feed material at a rate of around 600 gallons per minute. Therotating screen 40 constructed as defined above may be rotated at a ratewithin a second range of approximately 3-15 rpm.

When run at a high rate, or with very dense input material, the fluiddischarge to the collection pan 68 may overwhelm the capacity of theoutputs 70 and 72. In this situation, a bypass collector 100 comprisinga bypass outflow 102 may be employed as perhaps best shown in FIGS. 8and 9. The bypass collector 100 defines an upper lip 104 formed by abypass flange 106. As material within the collection pan 68 builds uptowards the input end 56 of the separator 20, material within thecollection pan 68 may build up beyond a maximum fill level 108 definedby the upper lip 104 of the bypass flange 106 as shown in FIG. 2.

As the material within the collection pan 68 exceeds the maximum filllevel 108, a liquid portion of this material flows over the upper lip104 of the bypass flange 106 and into the bypass collector 100. Thisbypass collector 100 is depicted in perspective in FIG. 3, and the upperlip 104 of the bypass flange 106 is visible in FIG. 7. The outflowexiting the bypass outflow 102 may be fed by way of a gravity drain orother systems and return to the source of the media to be separated,such as a settling pond.

FIG. 3 shows the input end 56 of the example separator 20 in furtherdetail and illustrates the shroud 34 (phantom line) and the exampledrive tension adjuster 38 and example drive belt 32. FIG. 3 furthershows that the input port 76 is defined by an input tube 110. Theexample input tube 110 is coupled to a cross frame member 112 in theexample separator 20. The cross frame member 112 further supports theshroud 34 and the input tube 110 by way of brackets 114 and supports theinlet tube. FIG. 3 also shows a water supply line 116 which will bedescribed in further detail below.

FIG. 5 shows the example separator 20 with the housing 22 and frame 24depicted by phantom lines to allow the support rollers or idler wheels44 and corresponding flanges 48 and 46 to be seen more clearly. FIG. 5further shows that the example separator 20 further comprises a watersupply line 116 that is coupled to a plurality of sprinklers 118. Thesesprinklers 118 allow the separator 20 to be operated in a self-cleaningmode in which water from the sprinklers 118 cleans the rotating screen40. FIG. 6 also shows the water supply line 116 and sprinklers 118, butfrom the output end 54. FIG. 6 also illustrates that the vanes 42 may beformed by a plurality of helical vanes 42A and 42B.

FIG. 6 also shows the elevation adjusters 52. The elevation adjusters 52of the example separator 20 allow the output end 54 to be elevated abovethe input end 56 with reference to a horizontal plane. The exampleelevation adjusters 52 thus allow a user to vary the elevation height120 of the output end 54 above the feet 122 of the separator 20. Aslight incline of the rotating screen 40 increases the efficiency of theoverall apparatus. However, the separator 20 may be configured tooperate anywhere between a horizontal or level orientation (0° withrespect to horizontal) or may be inclined up to 5° from horizontal.Stated alternatively, in the physical embodiment of the exampleseparator 20 as described above (a device of 10′ in overall length), theoutput end may raise approximately 4″ above the input end.

In one form, inclining the device from horizontal improves efficiency,while an incline in a first range of substantially between 0° and 5° ofa screen rotating at 3-15 rpm and having a diameter of about 3′ may bepreferred for common effluent consistencies although other dimensionsand rates will be used in other applications. In another form, thescreen 40 may be inclined at an angle in a second range of substantiallybetween 1° and 10°.

FIG. 9 illustrates that the example separator 20 defines four separateand distinct output ports for components or outflow material removedfrom the feed material. The output ports defined by the exampleseparator 20 comprise, from left to right, the bypass outflow 102, thefine material output 70, the coarse material output 72, and the verycoarse or solid material output 90. It may be desired to maintain theoutflow material from each outflow port separately.

As examples, the outflow material exiting the bypass outflow 102 may bechanneled back to the settling pond or other source. The fine materialoutput 70 provides a substantially liquid media which can be usedunprocessed or processed as required for a particular use. The outflowmaterial flowing out of the coarse material output 72 containssubstantially more solids than the outflow material flowing through thefine material output 70. The outflow material exiting the coarsematerial output 72 is thus more likely to require additional processingbefore this material can be reused. The outflow material exiting thevery coarse material output 90 should be substantially solid andcomprise a very small liquid component that can be used to the bestadvantage with or without additional processing as desired.

Referring now to FIG. 10 of the drawing, depicted therein is a secondexample hybrid rotary screen separator 220 of the present invention usedas part of a first example waste processing system 222. The examplehybrid rotary screen separator 220, which is depicted in further detailin FIG. 11, may be constructed to operate in a manner similar to that ofthe first example hybrid rotary screen separator 20 described above. Thefirst example waste processing system 222 is described herein by way ofexample only, and the screen separator 220 may be used as describedherein in many configurations of waste processing systems.

The principles of the present invention are of particular significancein the context of processing waste materials that are the byproduct ofanimal husbandry operations such as dairy farms, and that application ofthe present invention will now be described in further detail withreference to FIGS. 10 and 11.

Referring initially to FIG. 10 of the drawing, it can be seen that thefirst example waste processing system 222 comprises, in addition to thescreen separator 220, a sand separator 224 and a roller press 226. Thesand separator 224 may be a sand separator such as that described incopending U.S. patent application Ser. No. 13/351,214. The roller press226 is or may be a conventional roller press available for use in theexample waste processing system 222 as described herein.

The first example waste processing system 222 operates basically asfollows. A first material 230 comprising sand, solids, and water isinput to the sand separator 224. In a dairy operation, the firstmaterial 230 often contains sand because sand may be used as a beddingmaterial for the cows. The water portion of the first material may befrom rinse water, urine, or other water-based liquids used in a dairyoperation. The solids are typically manure and uneaten food such ascorn. Cleaning of dairy facilities creates a constant need to processthe first material 230 so that its components may be reused, recycled,further processed, and/or disposed of as appropriate.

The sand separator 224 processes the first material, typically usingwater 232, into a second material 234 primarily comprising sand and athird material 236 primarily comprising solids and water. The secondmaterial 234 may be recycled for use as bedding material or otherwiseappropriately reused or disposed of.

In the first example waste processing system 222, the third material 236is input to the screen separator 220. The screen separator 220 processesthe third material 236 to obtain a fourth material 240 commonly referredto as fine water, a fifth material 242 commonly referred to as coarsewater, and a sixth material 244 primarily comprising solids and coarsewater.

Fine water is a liquid that is primarily water and can be used withlittle or no processing in a modern dairy operation. In the firstexample waste processing system 222, the fourth material 240 is used asat least a portion of the water 232 used by the sand separator 224. Finewater typically has a first, relatively low, concentration of solidsand/or other impurities.

Coarse water is a liquid comprising water and solids, and it isdifficult to use coarse water in a modern dairy operation withoutadditional processing. In the first example waste processing system 222,the fifth material 242 is typically stored for further processing and/ordisposal as appropriate. Coarse water typically has a second, relativelyhigh, concentration of solids and/or other impurities. The firstconcentration of solids associated with the fourth material 240 is thustypically significantly lower than the second concentration of solidsassociated with the fifth material 242.

The sixth material 244 is simply a combination of coarse water and themajority of the solids present in the third material 236 and has athird, very high, concentration of solids and/or other impurities. Thesecond concentration of solids associated with the fifth material 242 isthus typically significantly lower than the third concentration ofsolids associated with the sixth material 244. It follows that the thirdconcentration of solids is higher than the second concentration ofsolids and significantly higher than the first concentration of solids.

In the first example waste processing system 222, the sixth material 244is input to the roller press 226. The roller press 226 processes thesixth material 244 to obtain a seventh material 250 primarily comprisingfine water and an eighth material 252 primarily comprising solids, withvery little liquid remaining in the eighth material 252. Like the fourthmaterial 240, the seventh material 250 is typically appropriate for usein a dairy facility without further processing and may be used as atleast a portion of the water 232 used by the sand separator 224. Theeighth material 252 may be further processed by composting or in ananaerobic digester and may be reused as fertilizer and/or an energysource.

FIG. 11 is a more detailed view of the example screen separator 220depicted in FIG. 10. As shown in FIG. 11, the example screen separator220 comprises a separator member or screen 260 defining a fineperforation region 262 and a coarse separation region 264.

The third material 236 is first processed by the fine perforation region262 to obtain the fourth material 240 and a transition material 266comprising solids and coarse water. The transition material 266 is thenprocessed by the coarse perforation region 264 to obtain the fifthmaterial 242 and the sixth material 244. A fourth concentration ofsolids associated with the transition material 266 is typicallysignificantly higher than the first concentration of solids associatedwith the fourth material 240 and the second concentration of solidsassociated with the fifth material 242. However, the fourthconcentration of solids associated with the transition material istypically significantly lower than the third concentration of solidsassociated with the sixth material 244.

Turning now to FIG. 12 of the drawing, depicted at 320 therein isanother example hybrid rotary screen separator system constructed inaccordance with, and embodying, the principles of the present invention.The example separator system 320 defines a system longitudinal axis Aand an overall length L. The example separator system 320 comprises ahousing assembly 322, a drive system 324, and a screen assembly 326.

The housing assembly 322 comprises a housing 330, a frame 332, and oneor more adjustment assemblies 334. This housing 330 encloses the workingportions of the separator system 320, and the frame 332 supports thehousing 330, the drive system 324, and the screen assembly 326 as willbe described in further detail below. The housing 330 and frame 332 maybe similar to or the same as the housing 22 and frame 24 described aboveand will not be described again in detail.

The example drive system 324 comprises a drive motor 340, an optionalreduction gear system 342, and a drive belt 344. The drive system 324may be similar to or the same as the drive assembly 26 described above.In particular, the drive belt 344 may be covered by a protective shroud346, and the motor 340 may be coupled to the housing 330 through a motorpivot (not shown in FIG. 12) and drive tension adjuster (not shown inFIG. 12). The example drive system 324 will not be described in detailherein again.

The example screen assembly 326 comprises a screen structure orseparator member 350 defining a separator chamber 352 having an inputend 354 and an output end 356. The example screen structure 350 issubstantially cylindrical, and a longitudinal axis of the screenstructure 350 is aligned with the system axis A. Operation of the driveassembly 324 thus causes axial rotation of the screen structure 350about the system axis A. The adjustment assembly or assemblies 334 allowadjustment of a height of the input end 354 relative to a height of theoutput end 356. Typically, the output end 356 will be higher than theinput end 354.

The example screen assembly 326 further comprises first and second vanestructures 360 and 362. A first perforation region 364 having a firstperforation configuration is associated with the first vane structure360, and a second perforation region 366 having a second perforationconfiguration is associated with the second vane structure 360. Thefirst perforation configuration comprises a plurality of holes in thescreen structure 350 that are sized, shaped, and spaced relative to eachother to allow relatively fine particulate materials and liquids to passfrom the separator chamber 352 to the exterior of the screen structure350. The second perforation configuration comprises a plurality of holesin the screen structure 350 that are sized, shaped, and spaced relativeto each other to allow relatively coarse particulate materials andliquids to pass from the separator chamber 352 to the exterior of thescreen structure 350. As one example, relatively fine particulatematerials may pass through an opening less than approximately 1millimeter, while relatively coarser particulate materials may passthrough an opening of approximately 10 millimeters.

The example first vane structure 360 defines a first spacing S1 andfirst length L1, and the second vane structure 362 defines a secondspacing S2 and a second length L2. The first and second spacings S1 andS2 define a distance along the system axis between longitudinally andradially adjacent points on the vane structures 360 and 362. The firstand second lengths L1 and L2 define an overall length of the vanestructures 360 and 362, respectively, and may be expressed in nominalterms or as a percentage of the overall length L of the separatorchamber 352. The first spacing S1 is typically greater than the secondspacing S2.

The example first and second vane structures 360 and 362 are rigidlyconnected to an inner surface 368 of the screen structure 350. Inparticular, the example vane structures 360 and 362 are one or more setsof helical screw blades that extend radially inwardly from the screenstructure inner surface 350 a. As an alternative, the vane structuresmay be implemented as one or more sets of helical screw blades thatextend radially outwardly from a shaft coaxially aligned with the screenstructure 350.

The example vane structures 360 and 362 are each comprised of twocontinuous, offset screw blades, but it is also possible that the screwblades of one or both of these structures 360 and 362 may be made ofdiscrete, discontinuous blade components. Additionally, a trailing edgeof the blades of the example first vane structure 360 is contiguous witha leading edge of the blades of the second vane structure 362, but thesestructures 360 and 362 may be dis-contiguous with each other. In anyarrangement, the purpose of the vane structures 360 and 362 is todisplace material along the separator chamber 352 from the input end 354to the output end 356 as will be described in further detail below.

Arranged below the screen assembly 340 are a first collection structure370 defining a fine material chamber 372 in fluid communication with afine material output port 374 and a second collection structure 380defining a coarse material chamber 382 in fluid communication with acoarse material output port 384. Optionally, a single collectionstructure defining a single material output port may be arranged underthe screen assembly. An overflow collection structure 390 defining anoverflow material chamber 392 in fluid communication an overflow outputport is arranged to collect liquids overflowing the fine materialchamber 372.

The fine material chamber 372 is arranged below the first perforationregion 364 of the screen structure 350 and is associated with the firstfiltrate stream generally described above. The coarse material chamber382 is arranged below the second perforation region 366 of the screenstructure 350 and is associated with the second filtrate streamgenerally described above. In particular, at least a portion of fluidmaterial displaced along the separator chamber 352 by the vanestructures 360 and 362 is diverted to the fine material output port 374and the coarse material output port 384 to form the first and secondfiltrate streams, respectively.

The example hybrid rotary screen separator system 320 operates generallyas follows. The drive system 324 is operated to cause axial rotation ofthe screen structure 350 and the vane structures 360 and 362 supportedby the screen structure 350. Feed material is introduced into theseparator chamber 352 through the input end 354. The first vanestructure 360 displaces the feed material along the first perforationregion 364 of the screen structure 350, and the second vane structure362 displaces the feed material along the second perforation region 366of the screen structure 350.

As the feed material is displaced through the separator chamber 352along the first perforation region 364 of the screen structure 350, finematerials and liquids pass through the perforations in the screenstructure 350 and are collected in the fine material chamber 372.Materials and liquids collected by the fine material chamber 372 passthrough the fine material output port 374 for further processing asgenerally described above.

As the feed material continues through the separator chamber 352 andinto the second perforation region 366 of the screen structure 350,coarser materials and liquids pass through the perforations in thescreen structure 350 and are collected in the coarse material chamber382. Materials and liquids collected by the coarse material chamber 382pass through the fine material output port 384 for further processing asgenerally described above.

Liquids, primarily water, and some solids that have not passed throughscreen structure 350 in the perforation regions 364 and 366 will exitthe separator chamber 352 through the output end 356 thereof. Inpractice, most of the solids passing through the separator chamber 352collect at the bottom of the screen structure 350 in a wad or mat thatis churned or rotated as the screen structure 350 rotates.

In the example separator system 320, the spacings S1 and S2 associatedwith the vane structures 360 and 362 are different, with the spacing S1being greater than the spacing S2 as described above. The first vanestructure 360 will thus displace material through the separator chamber352 at a first material displacement rate that is greater than a secondmaterial displacement rate associated with the second vane structure362. The first and second material displacement rates associated withthe first and second vane structures 360 and 362 mean that the feedmaterial moves more quickly along the first perforation region 364 thanacross the second perforation region 366.

As discussed above, the first perforation pattern associated with thefirst perforation region 364 allows liquids and finer particulatematerial to pass through the screen structure 350. The first materialdisplacement rate is thus predetermined based on the first spacing S1and the rate at which the screen assembly 326 is rotated as appropriatefor the characteristics of the feed material and the first perforationpattern. Similarly, the second perforation pattern associated with thesecond perforation region 366 allows liquids and more coarse particulatematerial to pass through the screen structure 350. The second materialdisplacement rate is thus predetermined based on the second spacing S2and the rate at which the screen assembly 326 is rotated as appropriatefor the characteristics of the feed material and the second perforationpattern.

In practice, the first material displacement rate may be high relativeto the second material displacement rate and still allow much of theliquid and fine particulate material to be removed from the feedmaterial along the first perforation region 364. After the feed materialhas moved along the first perforation region 364, however, much of theliquid and fine particulate material has been removed from the feedmaterial.

Predetermining the second material displacement rate such that it isless than the first material displacement rate allows the material moretime within the second perforation region 366. The second materialdisplacement rate thus allows more of the remaining liquid and thecoarse particulate material to be removed through the second perforationregion 366 of the screen structure 350. The use of two differentmaterial displacement rates thus allows an overall length L of thesystem 320 to be kept to a minimum.

While the example hybrid rotary screen separator 320 employs twodifferent perforation regions 364 and 366 and associated collectionchambers 370 and 380, more than two different stages each comprising aperforation region and collection chamber may be provided for aparticular operating environment. In this case, the spacings associatedwith each of the vane structures and the perforation patterns associatedwith each of the perforation regions would be predetermined to removemore particulate material of three different maximum sizes from the feedmaterial. Typically, but not necessarily, the size of the particulatematerial will increase and the material displacement rate will decreaseduring each successive stage.

In addition, although the example hybrid rotary screen separator 320employs two different perforation regions 364 and 366 with two differentmesh sizes, a significant portion of the benefits of the use of twodifferent regions can be obtained using a single mesh size. By the timethe material being process passes from the first perforation region 364to the second perforation region 366, much of the water within theprocessed material has been removed. The relatively smaller spacingbetween each of the adjacent vane structures in the second perforationallow the more time for the relatively smaller volume of fluid bypercentage in the processed material within the second perforationregion 366 to pass through the perforations, regardless of the size ofthe perforations relative to those of the first perforation region.

Referring now to FIGS. 13-18, depicted therein is a rotary screenseparator 420 comprising a first example cleaning system 422. Theexample rotary screen separator 420 may be any screen separator such asthe example hybrid rotary screen separators 20, 220, and 320 describedabove, and the rotary screen separator 420 will not be described hereinbeyond that extent helpful for a complete understanding of the operationof the cleaning system 422. As is conventional, the example rotaryscreen separator 420 comprises a screen 430 supported for rotationrelative to a frame 432. Further, the screen 430 defines an innersurface 434 and an outer surface 436, and holes 438 formed in the screen430 extend between the inner surface 434 and the outer surface 436. Atleast one flight of vanes 439 extend from the inner surface 434 towardsan interior of the screen 430. The vanes 439 define a maximum vane depthVDM which in turn defines a depth plane DP generally corresponding to aheight of material being processed within the rotary screen separator420.

As perhaps best shown in FIG. 18, the first example cleaning system 422comprises a blower 440 and one or more outlet assemblies 442. Theexample blower 440 comprises a blower inlet 450 and a blower outlet 452.A conduit system 454 is arranged to connect the blower outlet 452 to theoutlet assembly or assemblies 442.

The first example cleaning system 422 further optionally comprises ablower filter 456 and one or more gate valves 458. The blower filter orfilters 456 and gate valve or valves 458 are or may be conventional andwill not be described herein in further detail. The gate valve or valves458 may be manually operated or may be controlled by an electrical,pneumatic, hydraulic or other control system (not shown).

When the blower 440 operates, air is drawn along a flow path P extendingthrough the blower filter 456, the blower inlet 450, the blower outlet452, the conduit system 454, and the outlet assembly or assemblies 442.The gate valve or valves 458 are configured to prevent flow of fluidalong the flow path P when in a closed configuration and to allow theflow of fluid along the flow path P when in an open configuration. Inthe first example cleaning system 422, each gate valve 458 is arrangedbetween the conduit system 454 and one of the outlet assemblies 442.

FIG. 18 illustrates that the first example cleaning system 422 may beused with more than one rotary screen separator. In FIG. 18, the examplerotary screen separator 420 is indicated in solid lines, while optionalsecond and third rotary screen separators 420 a and 420 b are indicatedin broken lines. When the first example cleaning system 422 is used toclean only the rotary screen separator 420, only the outlet assembly 442is used. When the first example cleaning system 422 is further used toclean the optional second and third rotary screen separators 420 a and420 b, the conduit system 454 further connects the blower outlet 452 tosecond and third outlet assemblies 442 a and 442 b through optionalsecond and third gate valves 458 a and 458 b.

Referring now more specifically to FIGS. 13-17, the construction detailsof the first example outlet assembly 442 will be described in furtherdetail. If used, the optional second and third outlet assemblies 442 aand 442 b may be similar to the first example outlet assembly 442, andthe second and third outlet assemblies 442 a and 442 b will not bedescribed in further detail herein.

Further, although not depicted in FIGS. 13-17, multiple outletassemblies 442 may be employed with a single rotary screen separator.When multiple outlet assemblies 442 are used with a single rotary screenseparator, the outlet assemblies 442 may be angularly spaced about thesystem axis A1 and/or multiple outlet assemblies 442 may be located atthe same angular location but spaced along the length of the system axisA1.

As perhaps best shown in FIGS. 15 and 17, the example outlet assembly442 comprises a housing structure 460 and an inlet fitting 462. Theexample housing structure 460 defines a housing chamber 464 and anoutlet slot 466. The inlet fitting 462 defines an inlet opening 468. Inuse, the inlet fitting 462 is connected to the conduit system 454 suchthat air flows from the conduit 454, through the inlet opening, and intothe housing chamber 464. As will be described in further detail below,air flowing into the housing chamber 464 flows out of the housingstructure 460 through the outlet slot 466 and impinges the screen 430.As shown in FIG. 17, the outlet slot 466 defines an outlet slot lengthdimension SL and an outlet slot gap dimension SG.

The stream of air impinging on the screen 430 removes debris from boththe inner surface 434 and the outer surface 436 of the screen 430. Theuse of air to clean or otherwise remove debris from the screensignificantly reduces the amount of liquid (e.g., water) required foroperation of the rotary screen separator 420. Further, the use of theblower 440 to create a steady stream of relatively low pressure air issignificantly more efficient than the use of water and/or compressedair.

The example housing structure 460 comprises a housing wall 470 andproximal and distal end walls 472 and 474. The example inlet fitting 462is rigidly connected to, and the inlet opening 468 is formed in, theproximal end wall 472. The outlet slot 466 extends along the length ofthe housing wall 470 from adjacent the proximal end wall 472 to adjacentthe distal end wall 474. The example housing wall 470 is formed by firstand second housing members 475 and 476 joined together along a seam 478and to the first and second end walls 472 and 474. Alternatively, thehousing wall 470 may be formed in a single piece using othermanufacturing methods, such as extrusion. As another alternative, theentire housing structure 460, and possibly the inlet fitting 462, may becast or molded as a single piece. When extruded, cast, or molded, theoutlet slot 466 may be integrally formed at the same time, or thehousing structure 460 may be cut, punched, or otherwise worked to formthe outlet slot 466.

As perhaps best illustrated in FIG. 16, the housing chamber 464 formedby the example housing structure 460 defines a main portion 480, anintermediate portion 482, and a slot portion 484. The intermediateportion 482 extends between the main portion 480 and the slot portion484 and narrows such that dimensions (e.g., cross-sectional area) of thehousing chamber 464 are reduced in the slot portion 484 relative to themain portion 480 in the general direction that air flows out of theoutlet assembly 442. Further, the slot portion 484 in turn defines atransition portion 486, an outlet portion 488, and the outlet slot 466.The transition portion 486 is in direct fluid communication with theintermediate portion 482 and the outlet portion 488, and dimensions(e.g., cross-sectional area) of the transition portion 486 aresubstantially constant between the intermediate portion 482 and theoutlet portion 488. The outlet portion 488 is in direct fluidcommunication with the transition portion 486 and the outlet slot 466,and dimensions (e.g., cross-sectional area) of the transition portion486 are reduced between the transition portion 486 and the outlet slot466. An angle α is thus defined by inner surfaces of the housingstructure 460 on either side of the juncture between the transitionportion 486 and the outlet portion 488. The transition portion 486 andoutlet portion 488 define a flow plane F as shown in FIG. 16.

The geometry of the housing structure 460 is designed both to increasethe flow rate of air flowing along the flow path P near the outlet slot466 and to direct the air flowing out of the outlet slot 466 along theflow plane F. In particular, air flows out of the outlet slot 466 in aflow stream S (FIG. 14). The flow stream S defines a flow direction anda flow rate. The flow direction of the air forming the flow stream S isprimarily defined by dimensions of the slot portion 484 and, at leastinitially, extends along the flow plane F. The flow rate of the airforming the flow stream S is primarily defined by a source flow rate ofair entering the housing chamber 464 and by the dimensions of the outletslot 466.

As perhaps best shown in FIG. 14, the example outlet assembly 442 issecured to the frame 432 such that the flow stream S is directed at theouter surface 436 of the screen 430. At least a first portion of the airforming the flow stream S will remove at least a portion of any debrison the outer surface 436. Further, at least a second portion of the airforming the flow stream S will pass through the openings 438 in thescreen 430 and remove at least a portion of any debris on the innersurface 434 of the screen 430.

As is conventional, the screen 430 of the rotary screen separator 420 isrotated in a direction R about a screen axis A1 defined by the screen430 as shown in FIG. 14. The flow stream S is configured such that, asthe screen 430 axially rotates, the flow stream S intersectssubstantially the entire outer surface 436 in the circumferentialdimension and in the longitudinal direction. Accordingly, the flowstream S will remove debris from substantially the entire surface areaof both the inner surface 434 and outer surface 436 of the screen 430.

Further, outlet assembly 442 is arranged such that the flow plane F isdirected towards the outer surface 436 of the screen 430 at animpingement angle θ with respect to a line tangential to the outersurface 436 and extending through the point of intersection of the flowplane F and the outer surface 436. The flow stream S generally followsthe flow plane F and thus impinges the outer surface 436 at theimpingement angle β. As will be described in further detail below, thedirection of the flow stream S (as generally associated with the flowplane F and/or the impingement angle β) relative to the outer surface436 can be adjusted to enhance the ability of the flow stream S toremove debris from screen 430.

The foregoing description of the first example cleaning system 422indicates the parameters that may be controlled to control operation ofa cleaning system of the present invention include source flow rate ofthe source air, geometry and dimensions of the housing chamber 464,geometry and dimensions of the outlet slot 466, and angle (3 at whichthe flow stream S (or flow plane F) extends relative to the outersurface 436 of the screen 430. These parameters will be determined for aparticular rotary screen separator. In particular, parameters such asdimensions, operational speed, and feed material may vary for aparticular rotary screen separator, and a cleaning system of the presentinvention will be designed and operated to optimize cleaning of aparticular rotary screen separator.

In that context, the following Table A indicates primary parametersassociated with a first configuration of the first example cleaningsystem 422 as shown in FIG. 14A that may be varied for a particularoperating environment.

TABLE A First Second Preferred Preferred Parameter Example Range RangeSource Flow Rate (CFM) 100 50-150  25-250 Outlet Slot Length SL 139⅛″120-144″  96-168″ Outlet Slot Gap SG     0.045″ .040-0.075 0.025-1.00″Impingement Angle β  70° 60-80°   30-120°

A cleaning system constructed according to the primary parameters as setforth in the example column of Table A above results in the air movementof approximately 100 cfm per inch at 1.5 psi (or 41.5 in. of water).These standard operating parameters can be adjusted up or down dependingon the source of air available at a particular facility.

Alternatively, the following Table B indicates primary parametersassociated with a second configuration of the first example cleaningsystem 422 as shown in FIG. 14B that may be varied for a particularoperating environment.

TABLE B First Second Preferred Preferred Parameter Example Range RangeSource Flow Rate (CFM) 100 50-150 25-250  Outlet Slot Length SL 139⅛″120-144″ 96-168″ Outlet Slot Gap SG     0.045″ 0.040-0.050″0.030-0.060″  Impingement Angle β  90°  80-100° 67.5-112.5°

A cleaning system constructed according to the primary parameters as setforth in the example column of Table B above results in the air movementof approximately 100 cfm per inch at 1.5 psi (or 41.5 in of water).Further, in the example case where the impingement angle is 90°, theflow plane extends through the axis A of the screen 430. These standardoperating parameters can be adjusted depending on the source of airavailable at a particular facility.

More generally, for any cleaning system constructed in accordance withthe principles of the present invention, the flow rate per inch of anyparticular outlet slot will typically be approximately 100 cubic footper minute per inch of the outlet slot and may be within a firstpreferred range of approximately 80 to 120 cubic foot per minute perinch. The flow rate per inch of any particular slot should in any eventbe within a second preferred range of approximately 50 to 150 cubic footper minute per inch.

In addition to the primary parameters set forth in Tables A and B above,secondary parameters, such as the geometry of the main portion 480,intermediate portion 482, transition portion 486, and outlet portion 488of the housing chamber 464 are selected to optimize the flow stream S,generally and/or for a particular installation environment of a cleaningsystem of the present invention.

The air flow stream S exiting the example cleaning system 422 removesdebris from the outer surface 436 of the screen 430. In addition, atleast a portion of the air forming the air flow stream S passes throughthe openings 438 to remove debris from the inner surface 434 of thescreen 430. Additionally, FIG. 14 illustrates that the area at which theair flow stream S impinges on the outer surface 436 is above, andtypically well above, the depth plane DP determined by the depth of thevanes 439. In the example cleaning systems described herein, the airflow stream S impinges on the outer surface at a location on an upperhalf of the outer surface 436 of the screen 430. That is, the exampleair flow stream S of the example cleaning systems described hereinimpinges on the outer surface 436 at a location above a horizontal planeextending through the longitudinal axis A of the screen 430 duringnormal use of the example rotary screen separator 420.

Referring now to FIG. 19 of the drawing, depicted therein is a rotaryscreen separator 520 comprising a second example cleaning system 522. Aswith the example rotary screen separator 420 described above, theexample rotary screen separator 520 may be any screen separator such asthe example hybrid rotary screen separators 20, 220, and 320 describedabove and will not be described herein beyond that extent helpful for acomplete understanding of the operation of the second example cleaningsystem 522. As is conventional, the example rotary screen separator 520comprises a screen 530 supported for rotation relative to a frame 532.Further, the screen 530 defines an inner surface 534 and an outersurface 536, and holes 538 formed in the screen 530 extend between theinner surface 534 and the outer surface 536.

As can be seen in FIG. 19, the second example cleaning system 522comprises an air outlet assembly 540 and a liquid outlet assembly 542.The air outlet assembly 540 is or may be the same as the example airoutlet assembly 442 described above and thus will not be describedherein in further detail. The example liquid outlet assembly 542 maycomprise or be formed by sprinklers 118 described above and will alsonot be described herein in detail.

The second example cleaning system 522 thus may clean the screen 530 inan air mode using air, in a liquid mode using a liquid such as water, orin a combined mode using both air and water simultaneously. Typically,the example cleaning system 522 will operate in the air mode but willswitch to the liquid mode or the combined mode when the debris on thescreen 530 cannot easily or completely be cleaned using air alone.

Referring now to FIGS. 20 and 21 of the drawing, depicted therein is anoutlet assembly 620 that may be used in place of the outlet assembly 442as part of the first cleaning system 422 or in place of the outletassembly 540 as part of the second cleaning system 522 as describedabove.

The geometry of the example outlet assembly 620 is or may be similar tothat of the example outlet assembly 442 described above. However, ratherthan comprising a single inlet fitting like the inlet fitting 462 of theoutlet assembly 442, the example outlet assembly 620 comprises a housingstructure 630 and first and second inlet fittings 632 and 634. Furtherthe example housing structure 630 defines a first housing chamber 640, asecond housing chamber 642, a first outlet slot 644, and a second outletslot 646. The first and second inlet fittings 632 and 634 define firstand second inlet openings 650 and 652, respectively. In use, the inletfittings 632 and 634 are both separately connected to a conduit systemsuch as the conduit system 454 described above such that air flows fromthe conduit 454, through the first and second inlet openings 650 and652, and into the first and second housing chambers 640 and 642. Airflowing into the first housing chamber 640 flows out of the housingstructure 630 through the first outlet slot 644, and air flowing intothe second housing chamber 642 flows out of the housing structure 630through the second outlet slot 646.

More specifically, the example housing structure 630 comprises a housingwall 660, proximal and distal end walls 662 and 664, respectively, andan intermediate wall 666 connected to the housing wall 660 between theproximal and distal end walls 662 and 664. The example first inletfitting 632 is rigidly connected to, and the inlet opening 650 is formedin, the proximal end wall 662. The example second inlet fitting 632extends through the proximal end wall 662 and the first housing chamber640 to the intermediate wall 666. The example second inlet fitting 634is rigidly connected to, and the second inlet opening 652 is formed in,the intermediate wall 666.

The first outlet slot 644 extends along the length of the housing wall660 from adjacent the proximal end wall 662 to adjacent the intermediatewall 666. The second outlet slot 646 extends along the length of thehousing wall 660 from adjacent the intermediate wall 666 to the distalend wall 664. The housing wall 660 may be formed using any of the sametechniques discussed above with reference to the housing wall 470.

The use of two separate inlet fittings 632 and 634, two separate housingchambers 640 and 642, and two separate outlet slots 644 and 646 resultin two separate flow streams that impinge upon the screen of the rotaryscreen separator. The use of two separate housing chambers 640 and 642reduces differences in back pressure within and along the length of thehousing structure 630 and thus yields two separate flow streams having amore consistent flow rate of along the length of the housing structure630. In some situations, the provision of a more consistent flow ratealong the length of the housing structure 630 can result in improvedcleaning of the screen and thus justify the additional structurerequired by the example housing structure 630.

A cleaning system such as the example cleaning systems 422 and 522 asdescribed above may be operated continuously. Alternatively, either ofthe example cleaning systems 422 and 522 may also be operatedperiodically or asynchronously to save energy.

For example, FIG. 22 of the drawing depicts a rotary screen separator720 comprising a third example cleaning system 722. As with the examplerotary screen separators 420 and 520 described above, the example rotaryscreen separator 720 may be any screen separator such as the examplehybrid rotary screen separators 20, 220, and 320 described above. Theexample rotary screen separator 720 comprises a housing 730 and a screen732 but will not be described herein beyond that extent helpful for acomplete understanding of the operation of the second example cleaningsystem 722.

As shown in FIG. 22, the example cleaning system 722 comprises a blower740, a filter 742, an outlet 744, and a control system 746. As generallydescribed above, air is drawn by the blower 740 through the filter 742and out of the outlet 744 in an air flow stream S to remove debris fromthe screen 732.

The example control system 746 comprises a controller 750 and at leastone of a timer 752, a clean button 754, and a debris sensor 756. Theclean button 754 is accessible to the operator and generates a CLEANsignal when pressed. The debris sensor 756 is or may be an optical orother sensor capable of generating a DEBRIS signal when debris has builtup on the screen 732 of the rotary screen separator 720.

The example controller 750 may control the blower 740 to operate basedon a predetermined schedule (e.g., periodically) when the rotary screenseparator 720 is operating using the timer 752. An example of apredetermined schedule would be for the controller 750 to turn theblower 740 ON for 20 seconds and then OFF for 3-5 minutes.

In response to the asynchronous generation of the CLEAN signal by thepressing of the clean button 752 and/or of the DEBRIS signal by the oneor more debris sensors 756, the controller 746 may be configured tooperate the blower 740 for a preset time period (e.g., 20 seconds), foras long as the CLEAN and/or DEBRIS signals are present, or in a patternpredetermined effectively to remove debris from the screen of theseparator 720.

In addition, the controller 750 may be configured to perform logicoperations that operate the blower 740 based on the informationgenerated by one, two, or all of the timer 752, clean button 754, anddebris sensor 756.

In addition, a control system such as the example control system 746 maybe used in conjunction with the example cleaning system 442 describedabove in reference to FIG. 18. In that case, in addition to or insteadof operating the blower, the control system may be connected to gatevalves such as the gate valves 458 to appropriately clean one or more ofthe separators 420, 420 a, and 420 b. And a clean button such as theclean button 754 and/or debris sensor such as the debris sensor 756 maybe associated with each of the separators 420, 420 a, and 420 b. Such anarrangement optimizes the expense of the blower by allowing a singleblower to run continuously to service multiple separators or becontinual, timed, multiple continual, and multiple with timed on andoff, multiple with differing times on, or multiple with differing timesand offs. The exact control parameters will depend on factors such asthe specifics of the separator or separators, the nature of the materialbeing processed, and possibly energy (electricity) prices.

While the example outlet assembly 442 defines an elongate slot ofcertain preferred dimensions, multiple smaller slots or openings may beused in addition or instead. Further, a wider slot with more air atlower pressure may also be used.

While the present invention is illustrated by description of severalembodiments and while the illustrative embodiments are described indetail, it is not the intention of the applicants to restrict or in anyway limit the scope of the appended claims to such detail. Additionaladvantages and modifications within the scope of the appended claimswill readily appear to those sufficed in the art. The invention in itsbroader aspects is therefore not limited to the specific details,representative apparatus and methods, and illustrative examples shownand described. Accordingly, departures may be made from such detailswithout departing from the spirit or scope of the invention.

What is claimed is:
 1. A cleaning system for a screen of a rotary screenseparator, the screen having a substantially cylindrical shape extendingalong a longitudinal axis for a screen length, the outer surface of thesubstantially cylindrical screen being perforated to admit a flow ofliquid, the rotary screen separator for processing feed materialcomprising liquids and solids, the cleaning system comprising: ahousing, extending substantially the screen length parallel to andoffset from the longitudinal axis and situated outside of the outersurface of the screen defining at least one housing chamber, the housingchamber defining at least one inlet opening, and at least one outletslot having an outlet slot axis extending parallel to the longitudinalaxis and substantially the screen length, the outlet slot being in fluidcommunication with the housing chamber; and an air source; and a conduitsystem operatively connected between the inlet opening of the housingand the air source; wherein, when activated, air flows from the airsource through conduit system, through the inlet opening, into thehousing chamber, and out of the housing chamber through the at least oneoutlet slot the air forms a laminar flow within a flow plane as thelaminar flow impinges on the screen to remove debris from the screen. 2.A cleaning system as recited in claim 1, in which the cleaning systemcomprises a plurality of housings each defining at least one housingchamber, at least one inlet opening, and at least one elongate outletslot, where each elongate outlet slot is arranged to direct an air flowstream such that the air flow streams impinge on the screen to removedebris from the screen.
 3. A cleaning system as recited in claim 1,further comprising at least one water jet configured to spray water ontothe screen of the rotary screen separator.
 4. The cleaning system asrecited in claim 1, in which each of the at least one outlet slotdefines a slot length dimension of 96-168″ and a slot gap dimension of0.025-1.00″.
 5. The cleaning system of claim 1, wherein the housingdefines a plurality of housing chambers longitudinally arranged withinthe housing and wherein the at least one outlet slot comprises acorresponding plurality of slots, each slot defined by its correspondinghousing chamber and each slot axis being aligned to be colinear to eachother and parallel to longitudinal axis such that the correspondingplurality of slots extend substantially the screen length.
 6. Thecleaning system of claim 1, further comprising: a liquid outlet assemblycomprising: at least one sprinkler situated outside of the screen andoriented parallel to each of the longitudinal axis and the outlet slot,the spray issuing from the at least one sprinkler to strike the outersurface to form a spray pattern whose major axis is parallel to a linewhere the flow plane intersects the outer surface of the screen nearestto the outlet slot.
 7. The cleaning system of claim 6, wherein theliquid outlet assembly additionally comprises: a liquid outlet housingin fluid communication with the at least one sprinkler, the liquidoutlet housing being situated to extend substantially the screen lengthparallel to the longitudinal axis and residing outside of the outersurface of the rotary screen.
 8. The cleaning system of claim 1, furthercomprising: a debris sensor to: survey the outer surface of the screen;to detect the presence of debris thereon; and to generate DEBRIS signalsindicative of debris when detected; a controller to: receive the DEBRISsignals the debris sensor generates; to evaluate, at least, the DEBRISsignals the debris sensor generates; selectively to activate the airsupply source, in light of the received DEBRIS signals.
 9. A rotaryscreen separator for processing feed material comprising liquids andsolids, the rotary screen separator comprising: a screen having asubstantially cylindrical shape extending along a longitudinal axis fora screen length, the outer surface of the substantially cylindricalscreen being perforated to admit a flow of liquid; the rotary screenseparator defining an input port and an output port and including: adrive system for rotating the screen; and at least one vane structure; acleaning system comprising: a housing, the housing extendingsubstantially the screen length parallel to and offset from thelongitudinal axis and situated outside of the outer surface of thescreen and defining: one housing chamber, at least one inlet opening,and a plurality of outlet slots, each outlet slot having an outlet slotaxis aligned to be collinear one with each other outlet slot axis, theplurality of outlet slots extending parallel to the longitudinal axissuch that the plurality extends substantially the screen length, each ofthe plurality of outlet slots being in fluid communication with thehousing chamber; an air source for supplying air at the inlet opening toflow out of the plurality of outlets slot along a flow plane such thatthe air flow stream impinges on the screen to remove debris from thescreen, and a conduit system operatively connected between the inletopening of the housing and the air source; wherein operation of thedrive system to rotate the separator causes the at least one vanestructure to displace the feed material along the longitudinal axis; airflows from the air source through conduit system, through the inletopening, into the housing chamber, and out of the housing chamberthrough the plurality of outlet slots in at least one laminar air flowstream extending along a flow plane; and the housing is arrangedrelative to the screen of the screen separator such that the laminar airflow stream impinges on the screen to remove debris from the screen. 10.A rotary screen separator as recited in claim 9, in which the flow planeextends substantially parallel to the longitudinal axis of the screen.11. A rotary screen separator as recited in claim 9, in which the flowplane substantially extends through an axis of the screen.
 12. A rotaryscreen separator as recited in claim 9, in which the cleaning systemcomprises a plurality of housings each defining at least one housingchamber, at least one inlet opening, and at least one elongate outletslot, where each elongate outlet slot is arranged to direct an air flowstream such that the laminar air flow streams impinge on the screen toremove debris from the screen.
 13. A rotary screen cleaning systemcomprising: first and second housings each defining at least one housingchamber, at least one inlet opening, and at least one outlet slot havingan outlet slot axis, the outlet slot axis of the at least one outletslot of the first housing being collinear with the outlet slot axis ofthe at least one outlet slot of the second housing; the at least oneoutlet slot of the first housing and the at least one outlet slot of thesecond housing being arranged so that air issuing from the at least oneoutlet slot of the first housing and the at least one outlet slot of thesecond housing forms a laminar air flow such that the laminar air flowstream impinges on the screen.
 14. A rotary screen separator as recitedin claim 13, in which the cleaning system further comprises at least onewater jet configured to spray water onto the screen of the rotary screenseparator.
 15. The rotary screen separator as recited in claim 13, inwhich each outlet slot defines a slot length dimension of 96-168″ and aslot gap dimension of 0.025-1.00″.
 16. The rotary screen separator ofclaim 13, further comprising: a liquid outlet assembly comprising: atleast one sprinkler situated outside of the rotary screen and orientedparallel to the longitudinal axis, the spray issuing from the at leastone sprinkler to strike the outer surface to form a spray pattern whosemajor axis is parallel to a line where the flow plane intersects theouter surface of the screen in a line nearest to the outlet slot. 17.The rotary screen separator of claim 16, wherein the liquid outletassembly additionally comprises: a liquid outlet housing in fluidcommunication with the at least one sprinkler, the liquid outlet housingbeing situated to extend substantially the screen length parallel to thelongitudinal axis and residing outside of the outer surface of therotary screen.
 18. The rotary screen separator of claim 13, furthercomprising: a debris sensor to: survey the outer surface of the screen;to detect the presence of debris thereon; and to generate DEBRIS signalsindicative of debris when detected; and a controller to: receive theDEBRIS signals the debris sensor generates; to evaluate, at least, theDEBRIS signals the debris sensor generates; selectively to activate theair supply source, in light of the received DEBRIS signals.